Biology subjects

Hellert, J.

Publications and source records attributed to Hellert, J..

3 recordsLinked to original sources

bioRxiv2026

View Tomo: Context-aware targeting and analysis in electron cryo-tomography

Electron cryo-tomography (cryoET) resolves cellular structure in three dimensions, yet region selection is still typically based on two-dimensional projection images. Here, we introduce View Tomo, a workflow for rapid acquisition of low-magnification tomograms that enables screening, targeting and analysis in 3D. View Tomo tilt series are acquired in minutes at low dose (~3 e-/[A]2), producing high-contrast tomograms that remain compatible with subsequent high-resolution structural determination. We implemented View Tomo using an automated acquisition and reconstruction pipeline for rapid alignment. Across multiple viral and cellular systems, view tomograms revealed membrane remodelling events, assembly intermediates and cellular organisation that are difficult to identify in projection images. These data enabled targeted high-resolution imaging and quantitative analysis of spatial relationships within cells. View Tomo therefore extends cryoET workflows by improving target selection, enabling analysis of mesoscale organisation, and facilitating integration with correlative imaging approaches.

cell biology↗

bioRxiv2022

African swine fever virus - variants on the rise

African swine fever virus (ASFV), a large and complex DNA-virus circulating between soft ticks and indigenous suids in sub-Saharan Africa, has made its way into swine populations from Europe to Asia. This virus, causing a severe haemorrhagic disease (African swine fever) with very high lethality rates in wild boar and domestic pigs, has demonstrated a remarkably high genetic stability for over 10 years. Consequently, analyses into virus evolution and molecular epidemiology often struggled to provide the genetic basis to trace outbreaks while few resources have been dedicated to genomic surveillance on whole-genome level. During its recent incursion into Germany in 2020, ASFV has unexpectedly diverged into five clearly distinguishable linages with at least ten different variants characterized by high-impact mutations never identified before. Noticeably, all new variants share a frameshift mutation in the 3 end of the DNA polymerase PolX gene O174L, suggesting a causative role as possible mutator gene. Although epidemiological modelling supported the influence of increased mutation rates, it remains unknown how fast virus evolution might progress under these circumstances. Moreover, a tailored Sanger sequencing approach allowed us, for the first time, to trace variants with genomic epidemiology to regional clusters. In conclusion, our findings suggest that this new factor has the potential to dramatically influence the course of the ASFV pandemic with unknown outcome. Therefore, our work highlights the importance of genomic surveillance of ASFV on whole-genome level, the need for high-quality sequences and calls for a closer monitoring of future phenotypic changes of ASFV.

genomics↗

bioRxiv2022

Organisation of the orthobunyavirus tripodal spike and the structural changes induced by low pH and K+ during entry

Following internalisation, viruses employ the changing environment of maturing endosomes as cues to promote endosomal escape, a process mediated by viral glycoproteins. Specifically, we previously showed that both high [K+] and low pH promote entry of Bunyamwera virus (BUNV), the prototypical bunyavirus. Here, we used sub-tomogram averaging combined with AlphaFold, to generate a pseudo-atomic model of the whole glycoprotein envelope of BUNV. This allowed us to unambiguously locate the Gc fusion domain and its chaperone Gn within the floor domain of the spike. We also confirmed that low pH and high [K+] alters the viral glycoproteins, resulting in an activated intermediate state functionally-distinct from the highly ordered ground state, and we localize these changes to the floor domain. Biochemical data suggests that in this intermediate state the viral fusion loops are partially exposed and selectively interact with host cell membranes. Taken together, we reveal new mechanistic understanding of the requirements for virus entry.

microbiology↗